Electrode line structure having fine line width and method of forming the same

ABSTRACT

In an electrode line structure of a semiconductor device and a method for forming the same, the electrode line structure comprises a semiconductor substrate, and electrode lines, which are formed on the semiconductor substrate, and have an inclined end in the long axis direction. The electrode lines each include a first line unit, which substantially functions as an electrode line, a second line unit, which has an inclined end in the long axis direction and is separated from the first line unit by a predetermined distance, and an insulating plug, which is interposed between the first line unit and the second line unit and electrically insulates the first line unit from the second line unit.

This application is a divisional of U.S. application Ser. No.10/612,096, filed on Jul. 2, 2003, which relies for priority upon KoreanPatent Application No. 2002-57462, filed on Sep. 19, 2002, the contentsof which are herein incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device and a method ofmanufacturing the same, and more particularly, to an electrode linestructure having a fine line width and a method of forming the same.

2. Description of the Related Art

As the integration density of semiconductor devices increases, finecircuit patterns having a fine line width or electrode lines having afine line width are required. In particular, electrode lines such asword lines or bit lines are of the most widely used lines in a DRAM(dynamic random access memory) device, and the line width of theelectrode lines is considered to be the barometer of the level ofintegration and performance of the highly-integrated semiconductordevice.

Generally, electrode lines are formed by patterning a conductive layervia a photolithography process using an exposure-based optical systemcapable of achieving high-resolution.

However, as the integration density of the semiconductor devicesincreases exponentially, it is desirous for the word lines and the bitlines to have a line width not larger than the exposure limit, whichresults in the following problems.

With reference to FIGS. 1A to 1C, as shown in FIG. 1A, a conductivelayer 12 and a hard mask layer 14 are deposited on an upper portion of asemiconductor substrate 10 in order to form electrode lines, forexample, word lines. Thereafter, photoresist patterns 16 for definingthe word lines are formed by a known photolithography process. Theexpected line width of the word lines is not larger than the exposurelimit, and is currently about 0.1 μm. However, if the photoresistpatterns 16 having a line width not larger than the exposure limit aredisposed at fine intervals, edges of upper portions of the photoresistpatterns 16 become rounded due to the proximity effect and due to thephoto-interference generated when exposing the photoresist patterns 16.As a result, side walls of the photoresist patterns 16 tend to becomeinclined.

The hard mask layer 14 and the conductive layer 12, which are formedunder the photoresist patterns 16, are patterned using the abovephotoresist patterns 16 to form word lines 20. Since the word lines 20thus formed have the same profile as the photoresist patterns 16, edgesof upper portions of the word lines 20 are rounded, and side walls ofthe word lines 20 are inclined.

The side walls of the word lines 20 are inclined not only in the channellength direction (short axis direction of the word lines 20), as shownin FIG. 1B, but also in the channel width direction (long axis directionof the word lines 20), as shown in FIG. 1C. After removing thephotoresist patterns 16 using a known method, an insulating layer for aspacer (not shown) is deposited on an upper portion of the resultantstructure in order for a subsequent self-aligned contact step to beperformed. Then, the insulating layer to be formed into a spacer isetched by an anisotropic blanket etching method to form a spacer 22.Since the side walls of the word lines 20 become inclined during theetching step for forming the spacer 22, the insulating layer formed onthe inclined side walls of the word lines 20 is exposed to a largeamount of anisotropic etching gas. Therefore, as shown in FIG. 1C, onlya small amount of the spacer 22 remains on a portion of the side wallsof the word lines 20. The spacer 22 may be even partially removed at aportion of the inclined side walls of the word lines 20, therebyexposing a portion of the word lines 20. Particularly, in the case wherethe word lines 20 are made of a material that is susceptible to the wetetching chemical, such as SC1 (standard chemical 1), for example, amaterial containing tungsten, large portions of the word lines 20 areremoved during the subsequent wet etching step. A line defect istherefore generated in the semiconductor device due to the removal of alarge portion of the word lines 20.

FIG. 2 is a SEM (scanning electron microscope) photograph of aconventional gate line, and FIG. 3 is a photograph of a plan view of aconventional semiconductor device.

In a case where the word lines 20 are formed using the photoresistpatterns 16 having the fine line width and the fine space, it can beseen from FIG. 2 that the side walls of the word lines 20 are inclined.In FIG. 2, reference character A represents the inclined surface of theside walls.

When a subsequent etching step is preformed in the case where a portionof the spacer 22 has been removed, it can be seen from FIG. 3 that aportion of the word lines 20 are also removed. In FIG. 3, referencecharacter B represents defects of a line shape indicating the removedportion of the word lines 20.

SUMMARY OF THE INVENTION

The present invention provides an electrode line structure capable ofpreventing electrode lines of a semiconductor device from becomingpartially removed.

The present invention also provides a method of forming such anelectrode line structure.

According to an aspect of the present invention, there is provided anelectrode line structure of a semiconductor device comprising asemiconductor substrate; and electrode lines, which are formed on thesemiconductor substrate and have an inclined end in the long axisdirection. In the present invention, the electrode lines each include afirst line unit, which substantially functions as an electrode line, asecond line unit, which includes the inclined end in the long axisdirection and is separated from the first line unit by a predetermineddistance, and an insulating plug, which is interposed between the firstline unit and the second line unit and electrically insulates the firstline unit from the second line unit.

Further, the length of the electrode lines is greater than the ordinarylength of conventional electrode lines by a predetermined length. Theinsulating plug is formed at a predetermined position of each of theelectrode lines such that the first line unit has the ordinary length.The length of the second line unit is greater than the width of theelectrode lines, and less than the ordinary length.

The first line unit and the second line unit comprise a conductive layerand a hard mask layer, respectively. The conductive layer is, forexample, made of a material containing tungsten. The hard mask layer is,for example, made of a silicon nitride layer or a silicon oxynitridelayer. A spacer is formed on an inclined end in the long axis directionof the second line unit. The insulating plug can formed of the samematerial as the spacer. The electrode lines comprise, for example, wordlines or bit lines.

According to another aspect of the present invention, there is provideda method of forming an electrode line structure of a semiconductordevice. The method comprises depositing a conductive layer on asemiconductor substrate; depositing a hard mask layer on the conductivelayer; patterning the hard mask layer and the conductive layer to formelectrode lines; forming a hole of a line shape in a predeterminedportion of each of the electrode lines to cut the electrode lines,thereby defining a first line unit and a second line unit that areelectrically insulated from each other; depositing an insulating layerfor a spacer in the hole and on the electrode lines; and etching theinsulating layer using an anisotropic blanket etching method to form aspacer at an edge of the electrode lines.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detail preferred embodimentsthereof with reference to the attached drawings in which:

FIGS. 1A to 1C are elevated views of an electrode line structure of aconventional semiconductor device;

FIG. 2 is a SEM (scanning electron microscope) photograph ofconventional gate lines;

FIG. 3 is a photograph of a plan view of a conventional semiconductordevice;

FIG. 4 is a cross-sectional view of an electrode line structure of asemiconductor device according to a first embodiment of the presentinvention; and FIGS. 5A to 5C are cross-sectional views showing a methodof forming an electrode line structure of a semiconductor deviceaccording to a second embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention will now be described more fully with reference tothe accompanying drawings, in which preferred embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as being limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete and will fully conveythe concept of the invention to those skilled in the art. In thedrawings, the thicknesses of layers and regions are exaggerated forclarity. It will also be understood that when a layer is referred to asbeing “on” another layer or substrate, it can be directly on the anotherlayer or substrate, or intervening between the another layer and thesubstrate represent the same elements, and thus their descriptions willnot be repeated.

Embodiment 1

Referring to FIG. 4, electrode lines 130 are formed on an upper portionof a semiconductor substrate 100. The semiconductor substrate 100 may,for. example, comprise a bare silicon substrate, or an insulating layermay be formed on the semiconductor substrate 100. The electrode lines130 may, for example, comprise word lines or bit lines.

As in the conventional example, since the electrode lines 130 having afine line width are disposed at fine intervals, the side walls of theelectrode lines 130 are inclined. In a case where word lines are used asthe electrode lines 130 in the present embodiment, the length X1 in thelong axis direction of the electrode lines 130, that is, in the channelwidth direction, is greater than the ordinary length X2 of conventionalword lines by a predetermined length. Insulating plug 127 is formedwithin each of the electrode lines 130. The insulating plug 127 isformed at a predetermined position along the line that is capable ofdefining the ordinary length X2, so that the insulating plug 127 divideseach of the electrode lines 130 into a first line unit 120A, whichsubstantially functions as an electrode line, and a second line unit120B including an inclined side wall portion. The insulating plug 127cuts or bisects the electrode line 130 into the first and second lineunits 120A, 120B. Here, the length X3 of the second line unit 120B isgreater than the width of the electrode lines 130 or less than theordinary length X2.

The electrode lines 130 each include a conductive layer 105 and a hardmask layer 110. A tungsten metal layer or a tungsten silicide layer maybe used as the conductive layer 105. A silicon nitride layer may be usedas the hard mask layer 110.

A spacer 126 is formed at the side walls of the electrode lines 130 by aknown method. Since the spacer 126 is thinly formed at the side walls ofthe electrode lines 130, particularly, on the inclined side wall of thesecond line unit 120B, or is partially removed, the conductive layer 105may be partially exposed. Thus, the second line unit 120B may beaffected by a wet etching chemical through the exposed conductive layer105 in a subsequent wet etching step, and as a result, the conductivelayer 105 may be removed. However, since the second line unit 120B,which is insulated from the first line unit 120A by the insulating plug127 interposed therebetween, is, in essence, a dummy pattern, the firstline unit 120A, which substantially functions as a line, is not affectedby the properties of the second line unit 120B, even though theconductive layer 105 of the second line unit 120B may be partiallyremoved, or entirely removed. Further, since the conductive layer 105 ofthe first line unit 120A is surrounded, at the top portion by the hardmask layer 110, and at the side portion by the insulating plug 127, theconductive layer 105 of the first line unit 120A is prevented from beingremoved during the subsequent wet etching step.

Considering that the side walls of the electrode lines 130 are inclinedwhen the electrode lines 130 having the fine line width are formed, thelength of the electrode lines 130 is greater than the ordinary length bythe predetermined length in the electrode line structure according tothe present invention. Then, the insulating plug 127 is formed withineach of the electrode lines 130 so that the electrode lines 130 are eachdivided into the first line unit 120A, which substantially functions asa line, and the second line unit 120B, which has an edge having aninclined side wall and which functions as a dummy pattern.

Thus, even though the conductive layer 105 of the second line unit 120Bmay be exposed, and as a result, may be removed by the wet etchingchemical during wet etch, the first line unit 120A, which substantiallyfunctions as a line, is not affected, and thus operational defects inthe electrode lines 130 are prevented.

Embodiment 2

FIGS. 5A to 5C are cross-sectional views showing a method of forming anelectrode line structure of a semiconductor device according to a secondembodiment of the present invention. In the present embodiment, theelectrode lines are used as word lines.

Referring to FIG. 5A, a conductive layer 105 for word lines is formed onan upper portion of a semiconductor substrate 100. A gate insulatinglayer (not shown) is formed between the semiconductor substrate 100 andthe conductive layer 105. A tungsten metal layer or a tungsten silicidelayer may be used as the conductive layer 105. A hard mask layer 110 isformed on an upper portion of the conductive layer 105. The hard masklayer 110 electrically protects the word lines during a subsequent stepof forming a self-aligning contact, and may be formed of a siliconnitride layer or a silicon oxynitride layer. Thereafter, photoresistpatterns 115 are formed by a known photolithography process in order todefine the word lines having a fine line width and disposed at fineintervals. Edges of upper portions of the photoresist patterns 115 areremoved due to the proximity effect and due to the photo-interferencegenerated during the photolithography process, resulting in side wallsof the photoresist patterns 115 being inclined, as described above.

Referring to FIG. 5B, the hard mask layer 110 and the conductive layer105 are patterned using the photoresist patterns 115 as a mask to formword lines 120. Since the word lines 120 are patterned using thephotoresist patterns 115 as a mask, the shape of the word lines 120 ismodeled after the shape of the photoresist patterns 115. Thereafter, thephotoresist patterns 115 are removed. The length X1 of the word lines120 is preferably greater than the ordinary length X2 of conventionalword lines.

As shown in FIG. 5C, a predetermined portion of each word line 120 isetched to form a hole H. Further, the hole H divides each of the wordlines 120 into a first line unit 120A and a second line unit 102B, asdescribed above. The first line unit 120A has the ordinary length X2 andsubstantially functions as a word line. The second line unit 102B has aninclined outer edge surface, and is electrically insulated from thefirst line unit 120A. Thereafter, an insulating layer 125 for a spaceris deposited on the resulant structure. The width of the hole H may beless than two times the thickness of the insulating layer 125 so thatthe hole H is sufficiently buried by the insulating layer 125. Next, theinsulating layer 125 is etched by an anisotropic blanket etching methodto form a spacer 126 (refer to FIG. 4).

As described above, according to the present invention, considering thatthe outer side walls of the electrode lines are inclined when electrodelines having a fine line width are formed, the electrode lines of thepresent invention preferably have a length that is greater than theordinary length of the conventional electrode lines. Then, theinsulating plug or the hole is formed within each of the electrode linesso that the electrode lines are each divided into the first line unit,which substantially functions as a line, and the second line unit whichhas an edge having an inclined side wall functioning as a dummy pattern.

Thus, even though the conductive layer of the second line unit may beexposed, and as a result may be removed by the wet etching chemical, thefirst line unit, which substantially functions as a line, is notaffected, and thus the defects in the electrode lines are prevented.

While the present invention has been particularly shown and describedwith reference to preferred embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the appended claims.

1. A method of forming an electrode line structure of a semiconductordevice, comprising: depositing a conductive layer on a semiconductorsubstrate; depositing a hard mask layer on the conductive layer;patterning the hard mask layer and the conductive layer to formelectrode lines; forming a hole of a line shape in a predeterminedportion of each of the electrode lines to cut the electrode lines,thereby defining a separated first line unit and second line unit;depositing an insulating layer in the hole and on the electrode lines;and etching the insulating layer using an anisotropic etching method toform a spacer at a sidewall of the electrode lines.
 2. The method ofclaim 1, wherein the conductive layer comprises a material containingtungsten.
 3. The method of claim 1, wherein the hard mask layercomprises a silicon nitride layer or a silicon oxynitride layer.
 4. Themethod of claim 1, wherein the length of the electrode lines is greaterthan an ordinary length of conventional electrode lines by apredetermined length.
 5. The method of claim 4, wherein the hole isformed at a predetermined position of each of the electrode lines suchthat the first line unit has the ordinary length.
 6. The method of claim5, wherein the width of the hole in a direction perpendicular to a longaxis of each electrode line is less than two times the thickness of theinsulating layer.
 7. The method of claim 4, wherein a length of thesecond line unit is greater than a width of the electrode lines and lessthan the ordinary length.
 8. The method of claim 1, wherein theelectrode lines comprise one of word lines and bit lines.